If I wasn't as good natured I would take the bike. Having mentioned lighting to some ninjas before and such I would probably out of boredom take the bike and relocate it very close by and get freakie with it with some old Ulocks securely mounting the bike in so if the person that owned the bike only had a hacksaw and no keys (I'm keeping the keys to teach a lesson here on how to lock up the bike

) they would be spending a good 2 hours hacking away that mega lock of a mess and hopefully learn to lock the bike better next time. Oh god, I had a good laugh when I saw that pic.
Zero_Enigma